Alkaline nickel plating solutions

ABSTRACT

Addition agents for use in alkaline nickel plating baths which produce a brighter more ductile nickel electroplate. The addition agents are selected from the group consisting of substituted alkyl sulfonates wherein the alkyl radical contains from one-five carbon atoms and the substituents are selected from the group consisting of halogen, cyano and nitro.

nited States Patent lnventors Arthur H. Du Rose Richmond Heights; RobertL. Stern, Cleveland Heights, both of Ohio Appl. No. 752,170 Filed Aug.13, 1968 Patented Jan. 11, 1972 Assignee Kewanee Oil Company Bryn Mawr,Pa.

ALKALINE NICKEL PLATING SOLUTIONS 2 Claims, No Drawings [56] ReferencesCited UNITED STATES PATENTS 2,937,978 5/l960 Strauss et al 204/493,417,005 l2/l968 Baig 204/49 X 3,428,536 2/1969 Towle et al. 204/49Primary Examiner-G. L. Kaplan Attorney-John P. Hazzard ABSTRACT:Addition agents for use in alkaline nickel plating baths which produce abrighter more ductile nickel electroplate. The addition agents areselected from the group consisting of substituted alkyl sulfonateswherein the alkyl radical contains from one-five carbon atoms and thesubstituents are selected from the group consisting of halogen, cyanoand nitro.

This invention relates to the electrodeposition of nickel andnickel-cobalt alloys from alkaline plating solutions containing avariety of addition agents which includes certain substituted alkylsulfonates. More specifically, this invention is concerned withimproving the brightness of nickel deposits produced from alkaline bathsand increasing the limiting current density of said baths.

Alkaline nickel plating solutions have inherent advantages. The throwingpower of such solutions is almost invariably better than that observedin acid nickel solutions of the Watts or all-chloride variety. Forexample, the throwing power for alkaline nickel solutions using the BS]formula ranges from to 70 percent while that for the Watts solution is 5to +5 percent. Moreover, when proper preplating steps are followed, anumber of alkaline nickel formulations can be used to plate nickeldirectly on zinc base die castings. This provides a distinct economicadvantage as it avoids the need for the use of cyanide copper which notonly eliminates the costly problem of waste disposal but affords abetter corrosion resistance.

Many complex alkaline nickel plating solutions of various formulationshave been proposed and devised heretofore. Their use, however, has notbeen extensive for several reasons, primarily because of a limitedcurrent density, lack of ductility, high stress and lack of luster inthe deposit.

A variety of complexing agents has been used, see Saubestre's review inPlating, May 1958. Complexing agents which have been used singly or incombination with others are: NH OH (Brit. Pat. No. 512,484),triethanolamine as described in .I Met. Fin. Soc. Japan 11 (2) 55(1960), citrate (Brit. Pat. No. 880,786),hydroxyethylethylenediaminetriacetic acid (Brit. Pat. No. 1,022,073),and polyamines (U.S. Pat. No. 2,335,070). Also ammonia, citrate andpyrophosphate are used in combination as described in U.S. Pat. No.2,069,566 and Brit. Pat. No. 902,499. Similarly citrate, alkanolaminesand EDTA-type compounds are described in U.S. Pat. No. 2,773,818.

Other complexing agents such as glycolic acid, tartarate, acetylacetone,and ethylenediamine may be used. Even glycerol and oxalate can be usedalthough they are used in combination with other agents having morecomplexing ability and solubility.

Little work has been done on producing bright or semibright nickeldeposits from alkaline solutions. Brit. Pat. No. 902,499 proposes theuse of saccharin in combination with selenium, tellurium, arsenic orcoumarin, while Brit. Pat. No. 880,786 uses saccharin and a rather highconcentration of formaldehyde.

At first thought one might assume that any addition agent or brightenerthat is useful in acid nickel plating solutions would be also useful andeffective in alkaline nickel solutions. This assumption has been shownmany times not to be true. In fact many brighteners and addition agentswhich are effective in acid baths of zinc, tin, antimony copper and leadare ineffective and useless in the corresponding alkaline baths. Nickelis no exception. Table l is a list of compounds which exhibit little orno effect in alkaline nickel solutions.

TABLE I Phenylpropiolic acid (propiolic good) J-Methoxy-Il-phenylbutyne-l N-Propnrgyldlbcnzenesultonamidc Z-Propynyl) thiohenzothiazoleAllylsulfonute Diallyl allyl phosphonatc Allylarsonic acidB-Neopentylallyl alcohol 4-Mcthyl-4-pentene-2-ol Undecyl-lO ene-l-olMethylbuteneol Trinllylarnine Tetraallylethylenediamine N Allylsaccharin Cinnamyl alcohol Crotonic acid 17. Butanediol l8. Glycerinel9. Cyclohexunol 20. Fuchsin 21. Phenol 22. Nitroindazolc 23.Tetrnmethylene-bis-pyridinium chloride 24. Benzene sulfinic acid 25.Thiourea 26. Polyglycols and Pluronics It should be noted that compounds1-7, 12-14, -26 of above table are useful in acid nickel baths.

An important difference between the alkaline and acid nickel solutionsis that there appears to be very little, or consistent synergisticeffect due to the combination of so-called acid nickel control agentsand brighteners when they are used in combination in the alkaline nickelsolution. in acid nickel solutions the use of the brightener alone (Suchas fuchsin, ethoxylated propargyl alcohol, ethylenecyanohydrin, etc.)usually gives only a slight increase in or uneven deposit brightness andthe deposit tends to be brittle. When a control agent such asnaphthalene sulfonate or saccharin is added the brightness anduniformity of brightness are enhanced and the ductility is improved.Very seldom is the above combination of any benefit in the alkalinenickel solution. For example ethoxylated butynediol at 0.2 g./l. gives abright deposit up to about 70 a.s.f. At higher current densities thedeposit becomes duller. By acid nickel standards the ductility is poor.When 1 g./l. of saccharin is added the deposit becomes duller especiallyin the low-current density area and slightly less ductile. A similareffect, i.e., no improvement, is noted when 3 g./ 1. ofN,N-bis-(phenylsulfonyl)-4,4-biphenyldisulfonimide is added to analkaline nickel solution containing butynediol.Tetramethylene-bis-pyridinium chloride effects a streaked, semibright,very brittle deposit. The addition of N,N-bis-(phenylsulfonyl-4,4-biphenylenyldisulfonimide seemed to relieve thebrittleness somewhat but darkened the deposit. N- Propargyl saccharineffects a bright deposit at 0.1 g./l. with air agitation and theaddition of N,N'-bis(phenylsulfonyl)-4,4- biphenyldisulfonimide causesno improvement in ductility or brightness. For some reason N -allylsaccharin which is similar to N-propargyl saccharin when used in theacid bath, has no efiect when used in the alkaline solution.

In many cases as indicated above the addition of the sulfonate orsulfonamide control agent was harmful or of no help. In one case using 3cc./1. of allyl alcohol the deposit was semibright but the addition of asulfonamide increased the brightness. This was not so for B-chloroallylalcohol where only 0.5 cc./l. of the alcohol had to be used. The use ofN ,N'- bis(phenylsulfonyl)-4,4'-biphenyldisulfonimide will eliminatemisplating caused by high concentrations of ethoxylated propargylalcohol but just as good deposits are obtained when lower concentrationsof the acetylenic compound are used with no sulfonimide. Another casewhere a control agent was beneficial was forZ-butyne-l,4,-dithioethanol. These cases are rare however.

The use of certain sulfonate and sulfonamide control agents alone, inalkaline nickel solutions-has little effect compared to when these areused in acid solutions. The deposit from alkaline solutions with noaddition agents present usually has more sheen than those from acidsolutions. This may be why the addition of such agents as benzenesulfonate, saccharin or allyl sulfonate very seldom exhibit anyimprovement in brightness. Sometimes, as for dibenzenesulfonamide theuniformity of lustre is improved but the increase in luster is almostnegligible. Also the ductility is not improved.

The addition agents of the present invention comprise substituted alkylsulfonates wherein the alkyl radical contains from one to five carbonatoms and the substituents are selected from the group consisting ofhalogen, cyano and nitro. The effective concentration range for theseaddition agents of the instant invention is from 0.1 to 5.0 g./l. whilethe optimum concentration appears to be about 2 'g./l. for thesecompounds. One way in which these materials may be supplied to theelectroplating bath of the instant invention is to supply them in theform of the sodium salt, although the sulfonate of the instant inventioncan be supplied in any other manner familiar to those skilled in the artand the need not necessarily be the sodium salt thereof.

These addition agents of the instant invention are utilized to advantagein alkaline nickel plating processes. Such a nickel plating process canutilize any conventional source of nickel as used in the platingindustry such as NiC1 NiSo nickel sulfamate or NiBF wherein the pH isadjusted to between about 7.0 and l 1.0. Such plating baths can beoperated generally in the range from room temperature to 180 F.depending on the particular-type bath employed. Likewise, plating can beaccomplished in such baths at current densities of from about 5 to about100 amps per sq. ft.

Typical compounds falling within the scope of the instant invention andtheir effective concentration ranges as well as optimum concentrationsare given hereinafter.

6. 2,3-diiodopropylsull'onntc 0.l5.0 2.0

1 (I)CH cH, so,, Na

7. Z-chlorocthylsulfonate 0.1-5.0 10

ci-cH,-cH, -s0, Na

8. Z-Cynnoethancsulfonalc 0.1-5.0 2.0

As stated earlier in the specification, any conventional source ofnickel may be used in supplying the nickel for the plating bath for theinstant invention. For example, nickel chlorate, nickel sulfate, nickeltetraborate, nickel carbonate. nickel hydroxide, nickel sulfamate andthe like. Commonly complexing agents are used in such plating baths toproduce complex ions and such is suitable in the practice of the instantinvention.

We claim:

1. A nickel electroplating bath comprising an aqueous alkaline solutionhaving a pH of between about 7.0 and about 1 1.0 including at least oneelectrolyte containing nickel ions and having dissolved therein asufficient amount of a single brightening agent consisting of betweenabout 0.1 and 5.0 g./l. of a substituted alkyl sulfonate wherein thealkyl radical contains from one to five carbon atoms and thesubstituents are selected from the group consisting of halogen, cyanoand mtro.

2. The bath of claim 1 wherein 3-cyano-propanesulfonate is thebrightening agent, and is used in an amount of between the about 0.1 andabout 5.0 g./l.

2. The bath of claim 1 wherein 3-cyano-propanesulfonate is thebrightening agent, and is used in an amount of between the about 0.1 andabout 5.0 g./1.